Conveyance and End-of-Pipe Measures for Stormwater - FCM

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3. Conveyance and End-of-Pipe Best Management Practice 3.4 Selection of Best Management Practices 3.4 Selection of Best Management Practices 3.4.1 Concerns The nature of the downstream water body that will receive the stormwater discharge and the objectives identified for the application fundamentally influence the selection of best management practices. In some cases, high pollutant removal or environmental performance is needed to protect fully aquatic resources, and human health and safety within a particular watershed or receiving water. The areas of concern include the following: ■ Cold- and cool-water streams have habitat qualities capable of supporting trout and other sensitive aquatic organisms. The design objective for these streams is to maintain habitat quality by preventing stream warming, maintaining natural recharge, preventing bank and channel erosion, and preserving the natural riparian corridor. These objectives may be accomplished by promoting infiltration, evapotranspiration and capture and reuse of runoff, and minimizing the creation of impervious surfaces and the surface areas of permanent pools, preserving existing forested areas, bypassing existing base flow and/or spring flow, or providing shade-producing landscaping. ■ Sensitive streams (Design objectives are to maintain habitat quality through similar techniques used for cold-water streams, with the exception that stream warming is not as severe a design constraint. ■ Wellhead protection presents a unique management challenge. A key design constraint in protecting these areas that recharge existing public water supply wells is to prevent possible groundwater contamination by preventing infiltration of highly polluted runoff. At the same time, recharge of unpolluted stormwater may be needed to maintain the flow in streams and wells during dry weather. ■ Reservoir protection of watersheds that deliver surface runoff to a public water supply reservoir is of special concern. Depending on the treatment available at the water intake, it may be necessary to achieve a greater level of pollutant removal for the pollutants of concern, such as bacterial pathogens, nutrients, sediment, or metals. One particular management concern for reservoirs is ensuring that highly polluted runoff is adequately treated so drinking water is not contaminated. ■ Shellfish/beach protection requires that watersheds draining to specific shellfish harvesting areas or public swimming beaches receive a higher level of treatment to prevent closings caused by bacterial contamination from stormwater runoff. In these watersheds, best management practices are explicitly designed to maximize bacteria removal. 3.4.2 Selection Process Completing the following questions will help in selecting a best management practice or group of practices for a site and provides information on factors to consider when deciding where to locate the facilities. Other factors such as cost effectiveness and community values should also be considered. Figure 3–1 shows a flow chart of the selection process of best management practice facilities. Design examples demonstrating the application of the selection process are provided in Appendix B. Can the best management practice achieve the objectives and goals to be met at the site or is a combination of practices needed? Designers can screen the best management practices list using Table 3-4 to determine if a particular practice meets the following evaluation criteria category: rainfall capture, flow attenuation, water quality enhancement, major flow conveyance, and riparian corridor sustenance. At the end of this step, the designer can determine if a single practice or a group of practices is needed to meet the objectives and goals at that particular site. 30 Conveyance and End-of-Pipe Measures for Stormwater Control — July 2005
Do any physical constraints at the project site restrict or preclude the use of a particular practice? In this step, the designer screens the best management practice list to determine if the soils, water table, drainage area, slope, headwater conditions, land use, and ownership present at a particular development site might limit the use of a practice. Figure 3–1: Selection process for BMP facilities Do the remaining best management practices have any important community or environmental benefits or drawbacks that might influence the selection process? In this step, options are compared against each other with regard to operation and maintenance, riparian/aquatic habitat, community acceptance, cost, and other environmental and social factors. Conveyance and End-of-Pipe Measures for Stormwater Control — July 2005 31 3. Conveyance and End-of-Pipe Best Management Practice 3.4 Selection of Best Management Practices Figure 3–1 Selection process for BMP facilities
Page 1 and 2: National Guide to Sustainable Munic
Page 3 and 4: INTRODUCTION InfraGuide ® - Innova
Page 5 and 6: TABLE OF CONTENTS Acknowledgements
Page 7 and 8: ACKNOWLEDGEMENTS The dedication of
Page 9 and 10: EXECUTIVE SUMMARY Increasing urbani
Page 11 and 12: 1. General 1.1 Introduction Urbaniz
Page 13 and 14: Design storm — A rainfall event o
Page 15 and 16: 2. Rationale 2.1 Urban Stormwater T
Page 17 and 18: 2.2.3 Impacts on Stream Habitat Alo
Page 19 and 20: 3. Conveyance and End-of-Pipe Best
Page 21 and 22: Table 3-1: Evaluation Criteria for
Page 23 and 24: 3.3 Description of Best Management
Page 25 and 26: Table 3-3a: Conveyance Control Best
Page 27 and 28: Table 3-3b: End-of-Pipe Control Bes
Page 29: Table 3-3b: End-of-Pipe Control Bes
Page 33 and 34: 4. Applications and Limitations Tab
Page 35 and 36: Table 4-1a: Application of Conveyan
Page 37 and 38: Table 4-1b: Application of End-of-P
Page 43 and 44: 5. Evaluation of Facilities 5.1 Ope
Page 45 and 46: Appendix A: Stormwater Best Managem
Page 47 and 48: Figure A-7: Pervious pipe exfiltrat
Page 49 and 50: A.2.3 Constructed Wetlands Referenc
Page 51 and 52: Figure A-17: Cutaway of a Swirl Con
Page 53 and 54: Appendix B: Design Examples B.1 Des
Page 55 and 56: B.2 Design Example: Development of
Page 57 and 58: B.3 Design Example: Sedimentation F
Page 59 and 60: References AEP (Alberta Environment
Page 61 and 62: Sabourin Kimble & Associates, 1999.

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